The "first" link of the chain is also the latching link. The patent calls this piece a clutch. The cross pin that holds the chain on to the bar does not bear any of the strain when the wrench is in use. The chain is an improvement on the chain in Brock's July 12, 1887 patent (no. 366,451). The gripping surface on the bar is called a shoe, and has longitudinal grooves as well as transverse teeth.